This invention relates to sealing rings for sealing the ends of heat-insulated pipe units of the kind which consist of a pipe surrounded over the greater part of its length by at least one layer of heat-insulating foam material which is in turn enclosed by an outer jacket of fluid-impervious protective material, the end parts of the pipe projecting beyond the corresponding ends of the layer or layers of heat-insulating material and the ends of the jacket projecting likewise but for a shorter distance, so that annular recesses are formed in the ends of the pipe unit. Such pipe units will hereinafter be designated "pipe units of the kind referred to".
The invention also includes a heat-insulated pipe unit of the kind referred to having at least one end thereof sealed by a sealing ring according to the invention, as well as an improved heat-insulated joint between two pipe units of the kind referred to having their proximate ends sealed by sealing rings according to the invention.
The pipes of pipe units of the kind referred to may be metallic. The or each layer of heat-insulating material may be composed of a microcellular foam material, such as polyol isocyanate, polyurethane, phenolic foam or styrene foam, applied either by injection or by spraying. The outer jacket may be composed of a thermoplastic elastomer, such as polyethylene, P.V.C., a rubber-like compound, a butyl or styrene compound, or may be composed of a bitumatic compound and may be reinforced with Fibreglass (Trade Mark) or nylon.
A primary object of this invention is to provide improved means for sealing the ends of pipe units of the kind referred to, so as to prevent penetration of moisture from the outside into the heat-insulating layer or layers of the pipe units, thus destroying or reducing the effectiveness of the insulating material and, when the pipe units are connected together by heat-insulated joints, to isolate those pipe units from each other so that, in the event of a failure in one pipe unit, leakage into the or each adjoining pipe unit can be prevented.